In recent years, demand for a high capacity battery and capacitor capable of being miniaturized or lightened has been increasing along with development of a laptop computer, a mobile instrument such as a portable cellular phone, an electric vehicle, and the like.
For a high-capacity battery or capacitor, ones using a lithium ion conductive substance for an electrolyte, such as a lithium ion battery, a lithium-air battery, and a lithium ion capacitor have been studied conventionally.
Among those, a lithium ion battery has already been put in practical use, and, for an electrolyte thereof, a liquid electrolyte is used wherein an inorganic electrolyte such as lithium perchlorate is dissolved in an organic electrolyte fluid. A liquid electrolyte is problematic in safety, storage stability, long-term reliability, and the like, because there are possibilities of fluid leakage, vaporization, and the like.
In order to solve such a problem, a lithium ion conductive substance capable of being utilized in a solid state has been studied. In particular, a study of a solid lithium ion conductive substance that is a ceramic material has been advanced for a material with incombustibility that leads to safety, no water permeability, and a high water resistance in a Li-air battery that is expected for a next-generation battery. For a solid lithium ion conductive material, for example, Patent Document 1 and Patent Document 2 disclose a partially substituted material of Li1+x+yAlxTi2−xSiyP3−yO12 and a substance with a perovskite-type structure represented by LixTayTiO3 and a partially substituted material thereof. Furthermore, Non-Patent Document 1 and Non-Patent Document 2 disclose LiZr2(PO4)3 and Li1.2Zr1.9Ca0.1(PO4)3, respectively.